Iron-free self-braking electrode

ABSTRACT

A self-baking electrode for an electric furnace comprises a permanent tubular casing which extends beneath the furnace hood toward the furnace charge. A ram located over the top end of the casing can be retracted for inserting electrode paste and can be advanced for compacting the paste and extruding the baked portion of the electrode from the lower end of the casing. The lower end is articulated in a region which is engaged by electrode contact plates that exert a pressure on the casing and the baked electrode to permit extrusion at a controlled rate. The casing is surrounded by a mantle which is insulated and defines an annular gap around the casing. Hot gas is forced axially through the gap of the casing to melt and precure the electrode paste prior to the paste passing through the region of exit and electrode contact. The usual apparatus for advancing and retracting the whole electrode forming apparatus and electrode with respect to the furnace charge is also provided.

United States Patent [19]] Persson IRON-FREE SELF-BRAKING ELECTRODE [75] Inventor: John A. Persson, Gibsonia, Pa.

[73] Assignee: Pennsylvania Engineering Corporation, Pittsburgh, Pa.

221 Filed: Aug. 6, 1973 21 App]. No.: 385,825

Primary Examiner-Roy N. Envall, Jr. Attorney, Agent, or Firm-Fred Wiviott; Ralph G.

[ June 25, 1974 [57] ABSTRACT A self-baking electrode for an electric furnace comprises a permanent tubular casing which extends beneath the furnace hood toward the furnace charge. A ram located over the top end of the casing can be retracted for inserting electrode paste and can be advanced for compacting the paste and extruding the baked portion of the electrode from the lower end of the casing. The lower end is articulated in a region which is engaged by electrode contact plates that exert a pressure on the casing and the baked electrode to permit extrusion at a controlled rate. The casing is surrounded by a mantle which is insulated and defines an annular gap around the casing. Hot gas is forced axially through the gap of the casing to melt and precure the electrode paste prior to the paste passing through the region of exit and electrode contact. The usual apparatus for advancing and retracting the whole electrode forming apparatus and electrode with respect to the furnace charge is also provided.

29 Claims, 4 Drawing Figures This invention relates to a method and apparatus for making self-baking electrodes for use with electric furnaces.

Conventional self-baking electrode making apparatus comprises a vertically disposed cylindrical casing the lower end of which extends into the electric furnace. The upper end of the casing is open to permit workmen to insert chunks of carbonaceous paste which melts and ultimately cures to a solid state as a result of heat which is conducted upwardly from the cured portion of the electrode that emerges from bottom contact plates into the furnace. The cylindrical sections from which the casing is made have several inwardly directed fins to which the paste fuses near the input end. The fins provide for engagement between the casing and the uncured and cured portions of the electrode therein and the fins reinforce the electrode, conduct electric current from the contact clamps to the cured portions of the electrode and contribute toward conduction of heat from the cured portion to portions which are undergoing curing by heat.

Because the lower end of the casing from which the electrode emerges is normally in the hot environment of the furnace, the casing is consumed and new sections must be added at the top end. This is done by workmen on a floor above the furnace where they are protected. Conventionally, the electrode clamps are released to permit lowering of the self-baked electrode and the surrounding steel casing. Means are provided to adjust the distance of the casing and electrode with respect to the furnace to maintain a proper arc length with respect to the charge in the furnace.

Consumption of the casing and the fins therein result in iron being introduced into the melt within the furnace. Introduction of iron is undesirable when such products as high purity silicon and aluminum silicon are being refined in the furnace. To avoid introduction of iron into the melt, it has been customary to avoid use of self-baking electrodes and to use, instead, preformed or prebaked solid electrodes. The latter, of course, are much more expensive than self-baking electrodes and they require careful coupling of additional sections to make up for consumption of the electrode at the lower end.

One method of partially overcoming the introduction of ferrous metal into the furnace is to substitute for the usual radially inwardly directed reinforcing fins a lightweight metal framework which becomes embedded in the paste and rigidifies the electrode. The framework is free of the casing thus making it possible to advance the electrode at a somewhat higher rate than the casing is advanced in which case consumption of the casing is reduced. However, if the framework contains ferrous metal as usual, the melt in the furnace may still be somewhat contaminated, although to a lesser degree than with the method first discussed. One of the problems with this construction is that the framework must be as light as possible to minimize iron contamination in which case there may not be sufficient strength to reinforce the electrode adequately. A lightweight frame also conducts heat poorly so the paste may be cured at an unduly slow rate which results in loss of electrode strength where it emerges from the contact plates. The

framework is also not in contact with the casing so that electric current is not conducted directly from the electrode contact clamps to the plastic portion of the electrode and to the cured portion. The reduced heating and curing effect of the electric current in the central portion of the electrodes compels electrodes of reduced diameter.

SUMMARY OF THE INVENTION An object of the present invention is to provide electrode forming apparatus which minimizes introduction of metal out of which the apparatus is comprised into the molten charge within a furnace with which the electrode cooperates.

A further object of this invention is to provide apparatus which uses no fins, framework or other conductive or reinforcing members in the paste within the casing and yet provides for good thermal precuring and curing of the electrode paste before it emerges as a cured electrode from befow the contact plates.

A further object is to provide self-baking electrode forming apparatus in which the electrode may be formed without use of any fins, reinforcing framework or other structural element to conduct heat and electric current into the electrode, this object being achieved by providing electric contact members which engage the forming casing near its lower end in such manner as to have a circuit that is directed from the electrode contacts to the casing and to the solidified electrode.

A still further object is to provide for precuring of the electrode paste within the casing by surrounding it with a mantle that defines a concentric gap through which hot air or gas for curing may be circulated whereby conduction of heat from the furnace through the electrode itself'need not be relied upon exclusively to cure the electrode.

Still another object of this invention is to provide for reinforcing the electrode with non-metallic members such as wooden cores which introduce no ferrous contaminant into the furnace but which are converted to charcoal and have their pores filled eventually with carbon derived from the paste and from the hydrocarbons resulting from the curing process so that the entire cross sectional diameter of the electrode is conductive.

In general terms, the invention is characterized by an electrode forming cylindrical casing which has a free bore. A paste compacting and electrode extruding ram is situated above the upper open end of the casing. Retraction of the ram permits workmen to insert electrode paste into the casing and downward advancement of the ram extrudes the cured electrode from the bottom end thereof. The bottom end of the casing is provided with longitudinally disposed overlapping joints to make it somewhat inwardly resilient. The slits created by the overlaps are in turn covered with additional material to prevent leakage of paste and minimize leakage of hydrocarbon gas. There are electric contact plates surrounding the jointed end of the casing. The contact plates are under sufficient pressure to support the easing and the electrode therein but the pressure is not so great as to prevent the electrode being advanced under the influence of the ram at the top end as it becomes necessary for the electrodes to be extended to make up for that which is consumed at its lower end.

The substantially stationary casing is surrounded in concentric spaced relation by a mantle. Hot air or gas apparatus which will be set forth in reference to the drawing shortly hereinafter.

DESCRIPTION OF THE DRAWING FIG. 1 is a vertical elevation of the new self-baking electrode apparatus with parts in section and other parts in semi-section;

FIG/2 is a transverse section taken on a line corresponding with 2--2 in FIG. 1;

FIG. 3 is a partial section taken on a line corresponding with 3-3 in FIG. 1; and

FIG. 4 is a transverse section taken on a line corresponding with 4-4 in FIG. 1.

DESCRIPTION OF A PREFERRED EMBODIMENT Referring to FIG. 1, one may see that part of the electrode forming apparatus is above a floor and another part is below the floor. A region far below floor 10 is occupied by an electric furnace which .is not shown but the upper surface of the charge within the furnace is indicated by the reference numeral 11 near the bottom of FIG. 1. One of the hoods 12 of the furnace is shown fragmentarily and is seen to be positioned immediately beneath floor 10.

The electrode forming apparatus in FIG. 1 comprises a cylindrical metal casing 12 in which carbonaceous paste may be introduced for being baked into solid electrode. The casingmay be made up of a number of curved sections welded together. The interior of casing 12 is smooth and does not have the usual radially inwardly extending electrode supporting fins nor any other metallic reinforcement for the electrode that is formed therein. The formed, cured and solidified electrode portion 13 emerges from the bottom end of casing 12 under the influence of a ram head 14 at the top of the casing. Ram head 14 may be retracted from within the casing to permit workmen on floor 10 to introduce chunks of electrode paste into casing 12. Ram head 14 is driven by the connecting rod 15 of a fluid operated cylinder 16. Cylinder 16 can be pressurized to effectuate extrusion of electrode 13 from the bottom end of the casing. A mechanically operated ram could be substituted for the fluid operated ram if desired.

As shown in FIGS. 1 and 4, the lower end of electrode forming casing 12 is provided with circumferentially spaced axially extending overlapping joints 17 which make the end of the casing somewhat resilient and yielding to radially applied forces. The overlapping joints l7 prevent leakage of electrode paste, minimize loss of hydrocarbon gases and provide a large electric contact interface with exterior of casing 12. Overlapping joints 17 and casing 12 constitute an articulated structure which permits application of a gripping force by the casing on the electrode 13. Other resilient or articulated clamping mechanisms could be substituted for the one just described.

The lower end of the casing is surrounded by a plurality of electrode contact members 20. Contact members.

20 are carried on a pressure ring 21. Each contact is associated with a device 22 for applying pressure to the contact 20. The pressure applying devices 22 may comprise a housing 23 and a'plunger 24 surrounded by a shouldered sleeve 25. A spring 26 reacts against the shoulder and forces the plunger 24 against its associated electrode contact 20. A threaded collar 27 permits adjustment of spring pressure. The total force of the various plungers against the contact 20 is adequate to bring about a clamping action by the segments 19 of casing 12 against the electrode 13. The force is great enough to support the baked electrode 13 and the casing 12 and to prevent their inadvertent movement toward the furnace. The electrode 13 is actually restrained from inadvertent vertical movements by frictional force of the articulated casing bottom. When it is desired to feed more baked electrode into the furnace to make up for that which may be consumed in the electric arc, a force is applied to ram head 14 at the upper end of the casing and the frictional force at the lower end is overcome in which case the solid cured end 13 of the electrode is caused to extrude from the lower end of casing 12.

For self-baked electrode having a diameter of about 35 inches, it has been found that a holding force of about 30 to 40 pounds persquare inch on electrode contacts 20 is sufficient to prevent slippage of the electrode from the casing except when a predominating force is applied by means of ram 14.

The electrode contacts 20 are connected to a power distribution bus ring 30 by means of a plurality of tubular conductive members 31. Power distribution ring 30 may be provided with coolant fluid passages such as 32 and 33 which are in fluid communication with the interior of conductor tubes 31 to provide coolant to the hollowed out electrode contact elements 20 if desired. Power distribution ring 30 is connected by any suitable means to a plurality of conductor tubes 34 which are in turn in electrical continuity with a bus 35 to which a large number of paralleled flexible conductors 36 are connected. The flexible conductors 36 lead back to a bus terminal 37, shown in part, which connects to a terminal of a power transformer, not shown. The electric circuitry intervening between the electrode contacts 20 and the power transformer is substantially conventional and need not be described in greater detail.

Casing 12 is, of course, not fed into the furnace during operation thereof nor during forming an electrode therein. The only time casing 12 moves is when it is advanced jointly with the electrode for the purpose of establishing the position of the electrode tip as will be described subsequently.

Casing 12 is surrounded by a cylindrical mantle 40 which is moved bodily with the casing to adjust the position of the tip of the baked electrode 13 within furnace charge 11. Sections taken through the mantle 40 may be seen in FIGS. 2 and 3. Mantle 40 comprises an outer cylindrical shell 41 and an inner cylindrical shell 42 in concentric spaced relationship therewith. There are layers of thermal insulation 43 and 43 on the inside surface of inner shell 42 and the outer surface of the upper casing 12 section. The two layers of thermal insulation are radially spaced so as to define a concentric gap 44 around the casing as can be seen in FIGS. 1-3. Insulating layers 43 and 43' terminate near the lower casing 12 section and the mantle 42 and casing 12 then form an uninsulated gap 44 which is continuous with gap 44. Hot air or other hot gas is forced downwardly through gap or duct 44, 44' from an encircling plenum 45 which is supplied with pressurized hot air through a duct 46 leading to a blower 47. By means of a conduit 48, the intake side of blower 47 is connected to a source of hot air, such source not being shown. The source may be an ordinary hot air furnace in which fuel is burned in a combustion chamber that is in heat exchange relation with air circulating over it. The hot air is drawn into the system by fan 47 and forced through duct 44 in heat exchange relationship with casing 12 at the lower end portion of the mantle 40 only so that the electrode paste within the casing in the lower end portion is subjected to heat for precuring. The temperature of the air is sufficient to bake the contained paste at about 450C. The hot air enters duct 44 through annular gap 49 at the top thereof and the hot air exits from the duct at the lower end 50 inside of the furnace hood. Because the hot gases emerge under the furnace hood, it is also possible to use rather completely oxidized hot gases of combustion directly for heating the lower part of electrode casing 12 instead of heating air by passing it over a combustion chamber.

The mantle 40 is supported at its upper end by a ring 50 which connects to the outer shell 41 of the mantle by means of several gusset plates 51 which may be welded to shell 41 and ring 50. Ring 50 is in turn carried by a frame 52 which is supported on an electrode elevating and lowering hydraulic cylinders 53, one of which is visible in FIG. 1. This cylinder may also be of the pneumatic type. In any event, by means which are not shown, the cylinder 53 may be actuated to raise or lower ring 50 and thereby raise and lower electrode casing 12, the electrode 13 and surrounding mantle 40 jointly with casing 12. These components are jointly raised or lowered in accordance with the need for adjusting current flow to the furnace charge by increasing or decreasing the length of the are between the tip of the electrode 13 and charge 11 or by adjusting the distance in which the electrode projects into the charge or a slag layer thereon if the furnace is of the thermal conductive type rather than an arc furnace. The servo system for sensing voltage drop across the arc and actuating electrode positioning cylinder 52 accordingly is not shown since this system may be conventional and is well known to those skilled in the art.

When casing 12 and mantle 40 are raised or lowered together there is no slippage between electrode 13 and the clamping arrangement at the lower end of casing 12. Under these circumstances the electrode contact elements are also raised and lowered with the casing and mantle as are the conductors 34 and flexible conductors 36 by virtue of the latter being supported on a post 54 which is connected to frame 52 through floor 10. A set of circumferentially spaced guide rollers 55 are journaled for rotation on associated stationary brackets 56. Rollers 55 guide and maintain the alignment of mantle when it is undergoing bidirectional vertical movements in response to signals that indicate the need for a change in the arc length. Rollers 55 ride on hardened bearing strips 57 which may be welded on the external surface of the outer mantle shell 41. Brackets 56 are supported ona base 58 which is mounted on furnace hood 12 although it could be mounted on any stationary structural member of sufficient strength. Beneath rollers is a duct 59 which is maintained at positive pressure and which has an air exit passageway 60 for the purpose of preventing gases from the furnace leaking to the space above floor 10. This is merely exemplary since a furnace fume seal can take a variety of forms as is known to those skilled in the art.

Electrode casing 12 and the self-baked electrode 13 therein'is indicated to be comprised of several regions which are in various states of curing. The regions are indicated by brackets. The region embraced by lowermost bracket 13a is that in which the electrode is substantially fully cured and hardened throughout. In region 13b, the electrode paste is in a substantially unbaked state near the top and a substantially fluid state near the bottom. Electrode paste additions are made in region 13c.

Operation of the electrode forming apparatus is as follows. Assume that the furnace is operating and that electrode exists within casing 12 in various states of curing. Assume that so much of the lower tip of electrode 13 has been consumed as to make it desirable to extend the electrode further into the furnace. This is done by actuating cylinder 16 to cause ram head 14 to force the electrode downwardly for greater emergence from casing 12. The downward force need only be sufficient in combination with the weight of the electrode to overcome the frictional holding force applied by the pressurized contact plates 20 acting on the articulated or slotted lower end of casing 12. When the baked electrode extends sufficiently far from the casing 12, ram head 14 is retracted so as to expose the cavity in the top part of casing 12 which has been created by extrusion of electrode from the bottom part. Workmen on floor 10 may then introduce more electrode paste into the top interior void in casing 12. Although not previously discussed in detail, there are also provided wooden core sections 61 which are connected to each other by the workmen prior to introduction of additional paste into the top of casing 12. Paste is introduced around the core. The cores may be connected by means of threaded projections on one being received in the opposite end of the next consecutive section or the wooden cores may be connected by providing them with tapered wooden plug extensions that register in a correspondingly tapered hole in an adjacent section. Any method of connection that does not use ferrous elements may be used. The paste in portion of the electrode subsequently melts due to the heat from the hot air in duct 44 defined by mantle 40 and the paste fuses around the wooden core to form a relatively baked mass in portion 13 a. As the paste is extruded downwardly in casing 12, it gets hotter and hotter as a result of heat exchange with the hot air in duct 44 and continues to solidify and at the same time the volatile hydrocarbons are liberated. The volatile hydrocarbons are sealed off against upward exit by the molten paste so they are forced downward into the pores of the electrode in a region below the contact plates where the electrode is more thoroughly cured and hardened but porous enough to accept the hydrocarbon gases. Eventually, these gases become sufficiently heated by conduction from the furnace up the electrode to fractionate and produce carbon with deposits in the pores of the more completely cured portions of the electrode. This improves electric conductivity of the exited solidified and cured electrode portion below the contact plates which electrode may attain a temperature of about l,lOOC which is sufficient to crack the gases and deposit carbon. Even before the electrode material reaches this temperature, the wooden plugs 61 become carbonized and porous and capable of receiving gases which fractionate and deposit carbon in their pores. This further contributes to the electrical conductivity of the electrodes.

Continuous adjustment of the electrode tip position in response to current and voltage sensitive sensors, not shown, is obtained, as discussed generally above, by moving mantle 40, the casing 12, the electric contact elements 20, the fan 47, its associated duct work and the supporting frame 50 bodily in one vertical direction or another by actuation of fluid operated cylinder 53. These movements are rather small amplitude and do not result in moving casing 12 substantially closer to the intensely heated part of the furnace where melting thereof might occur so as to introduce ferrous contaminants into the melt.

Good electrical contact is maintained between the casing and electrode at all times including those times when electrode is being forced out of casing 12 in opposition to the frictional holding force which exists between the bottom articulated part of the casing and the electrode.

Although a preferred embodiment of the invention has been described in considerable detail, such description is to be considered illustrative rather than limiting, for the invention may be variously embodied and is to be limited only by interpretation of the claims which follow.

I claim:

I. Self-baking electrode apparatus for use with an electric furnace, said apparatus comprising:

a. a metal casing having an opening in one end for electrode exit and an opening remote therefrom for introduction of electrode forming material into said casing which material first becomes plastic and is then successively baked to a hardened state in which it emerges from said one end,

b. means for supporting said casing relative to said furnace,

c. means for restraining said electrode against substantial emergence from said casing, and

d. means for applying a force on said electrode forming material within said casing to thereby overcome said restraint of said electrode and cause it to emerge from said casing.

2. The apparatus set forth in claim 1 wherein:

a. said casing has a substantially uniform cross sec tional shape and a substantially smooth and clear interior over its entire length.

3. The invention set forth in claim 1 including:

a. electric contact means engaged with said casing,

b. said restraining means including articulated means surrounding and engaged with a substantially solidified portion of said electrode, said articulated means being interposed between said contact means and said electrode and said articulated means being adapted to yield toward the center of said electrode under the influence of force applied through the agency of said contact means.

4. The invention set forth in claim 1 wherein:

a. there are a plurality of perimetrally disposed axially extending overlapping jointed segment means in said one end region of said casing, said segment means being yieldable toward the electrode in said casing.

5. The invention set forth in claim 1 including:

a. means defining a duct for conducting hot gas in heat exchange relationship with said casing, said duct surrounding at least the lower end portion of said casing, said hot gas effecting prebaking of said electrode material.

6. The invention set forth in claim 5 wherein:

a. said casing is vertical and said casing supporting means also supports said duct means, said supporting means being constructed and arranged for executing bidirectional vertical movements to thereby jointly move said duct, casing and electrode in relation to a furnace, and

b. means for moving said supporting means.

7. The invention set forth in claim 6 including:

a. blower means for forcing heated gas generally downwardly along said casing means.

8. The invention set forth in claim 1 including:

a. means defining a duct surrounding said casing over a substantial part of its length,

b. thermal insulation interposed between said duct and said casing in the upper portion thereof, the lower portion of said casing being uninsulated so that hot gas conducted by said duct will precure the electrode in the lower portion of said casing.

9. The invention set forth in claim 1 including:

a. a mantle surrounding said casing in spaced relationship to define a passage for heated gas, said mantle extending a substantial distance over the length of said casing,

b. said mantle having an inlet for admitting heated gas to one end of said passage and an exit remote therefrom, and

c. means for coupling a source of hot gas to said inlet.

10. The invention set forth in claim 9 including:

a. thermal insulation in said passage next to said casing and disposed to substantially limit heating of the paste in said casing adjacent to the one end portion thereof.

11. The invention set forth in claim 9 wherein:

a. said mantle is supported jointly with said casing by 'said supporting means, said supporting means being constructed and arranged for moving bidirectionally vertically to thereby enable joint movement of said mantle, casing and electrode in respect to a furnace, and

b. means for moving said supporting means.

12. The invention set forth in claim 11 including:

a. blower means supported for moving jointly with said mantle for blowing said hot gas downwardlyalong said casing.

13. The invention set forth in claim 1 wherein:

a. said means for applying force on said electrode forming material comprises ram means adapted to register in said remote opening of said casing, and

b. means operatively coupled with said ram means for forcing said ram means against said electrode material to expel said electrode from said casing and to retract said ram means to allow introduction of electrode forming material in said casing.

14. The invention set forth in claim 13 wherein:

a. said last named coupled means is a pressure operated cylinder.

l5. Self-baking electrode apparatus for use with an electric furnace, said apparatus comprising:

a. a vertically disposed metal casing having a lower open end and an opening in its upper end for introduction ofv electrode forming material which becomes plastic and is successively baked to a hardened state in which it emerges from said lower end,

b. support means for supporting said casing with its lower end positioned for cooperation with said furnace,

c. clamp means constructed and arranged to bear against said electrode in its region of emergence where it is in a substantially hardened state,

d. first means for applying a force on said clamp means to clamp said electrode against descending from said casing under the influence of gravity, and

e. second means for applying sufficient force to said electrode through said upper opening in said casing to overcome the clamping force on said clamp means so as to cause said electrode to emerge further from said casing.

16. The invention set forth in claim wherein:

a. said clamp means include a plurality of perimetrally disposed axially extending segments near the lower end of said casing, said segments being yieldable toward said electrode for frictional engagement therewith.

17. The invention set forth in claim 15 including:

a. means defining with said casing a passage extending along said casing over a substantial portion of its length, said passage being for conducting heated gas along the outside of said casing to prebake said electrode material therein, a portion of said passage being in intimate heat exchange relation with a lower end portion of said casing, and

b. means for admitting heated gas to said passage.

18. The invention set forth in claim 17 wherein:

a. said passage defining means has an opening near the lower end of said casing for permitting gas to exit from said passage.

19. The invention set forth in claim 17 including:

a. means for moving said support means in opposite vertical directions,

b. said passage defining means being supported by said support means and said casing being supported from said passage defining means whereby said electrode may be adjusted vertically with respect to said furnace to alter the distance between said electrode and contents of said furnace while said electrode remains clamped to said casing.

20. The invention set forth in claim 15 including:

a. a plurality of overlapping, axially extending segments firming the lower end of said casing, plate means disposed over the joints between the segments of said casing,

b. electric contact means pressed against said plate means,

c. said first force applying means acting on said contact means.

21. The invention set forth in claim 20 including:

a. means connected with said contact means for connecting said contact means to a source of electricity.

22. Self-baking electrode apparatus for use with an electric furnace, said apparatus comprising:

a. a vertically disposed tubular metal casing supported with its lower end in cooperative position relative to said furnace,

b. the upper end of said casing providing access for introducing electrode forming material into said casing, said material being characterized by being in a plastic state when in a certain temperature range and by being cured to a hardened state when in a certain relatively higher temperature state, said electrode extending from said lower end of said casing in a substantially hardened state,

c. means for frictionally engaging a portion of said electrode in a region where it is hardened substantially near the lower end of said casing whereby to restrain said electrode selectively s'tationarily in said casing in opposition to the force of gravity on said electrode, and

d. means for applying sufficient force to said electrode forming material at the upper end of said casing to overcome said frictional force and extend said electrode further from said casing.

23. The invention set forth in .claim 22 wherein:

a. said casing includes means defining at least one overlapping joint at the lower end thereof to enable said casing to yield toward said electrode for said frictional engagement,

b. means conforming substantially to the contour of said casing and disposed over said joint means,

c. electric contact means in electric current exchange relation with said conforming means,

d. means for applying a force on said contact means which is transmitted by the same to said plate means for causing said casing means to yield and effect said frictional engagement.

24. The invention set forth in claim 23 wherein:

' a. said last named force applying means includes rigid ring means surrounding said contact means,

b. plunger means supported on said ring means and projecting against said electric contact means, and

0. spring means biasing said plunger means toward said contact means.

25. The invention set forth in claim 22 including:

a. a mantle extending a substantial distance over said casing and being in spaced relation therewith to define a gas flow passage,

b. means for forcing heated gas through said passage longitudinally of said casing to thereby supply additional heat to said electrode material for prebaking the same.

26. A method of making and using a self-baking electrode in association with an electric furnace, comprismg:

a. introducing unbaked carbonaceous material into the upper end of a vertically disposed tubular casing whose lower end cooperates with a furnace and from which lower end a baked and hardened portion of said electrode extends,

b. directing heated gas over the exterior surface of said casing to prebake and cure said material near said lower end portion while at the same time heating said lower hardened portion by conducting current therethrough and by radiation and conduction of heat resulting from electric activity in said furnace,

c. applying sufficient compressive force to a portion of said casing at the lower end thereof where said electrode is in a substantially hardened state to frictionally restrain said electrode against emergence from said casing under the influence of gravity, and

d. periodically applying a vertically directed force on the material at the upper end of said casing to overcome said frictional restraint and cause said lower hardened electrode portion to extend further from said casing.

27. The method set forth in claim 26 including:

a. inserting wood core sections in sequence substantially centrally of said casing at the upper end thereof to provide a wooden spine through said electrode for strengthening the same, said unbaked carbonaceous material being inserted at the upper baked electrode portion. 

1. Self-baking electrode apparatus for use with an electric furnace, said apparatus comprising: a. a metal casing having an opening in one end for electrode exit and an opening remote therefrom for introduction of electrode forming material into said casing which material first becomes plastic and is then successively baked to a hardened staTe in which it emerges from said one end, b. means for supporting said casing relative to said furnace, c. means for restraining said electrode against substantial emergence from said casing, and d. means for applying a force on said electrode forming material within said casing to thereby overcome said restraint of said electrode and cause it to emerge from said casing.
 2. The apparatus set forth in claim 1 wherein: a. said casing has a substantially uniform cross sectional shape and a substantially smooth and clear interior over its entire length.
 3. The invention set forth in claim 1 including: a. electric contact means engaged with said casing, b. said restraining means including articulated means surrounding and engaged with a substantially solidified portion of said electrode, said articulated means being interposed between said contact means and said electrode and said articulated means being adapted to yield toward the center of said electrode under the influence of force applied through the agency of said contact means.
 4. The invention set forth in claim 1 wherein: a. there are a plurality of perimetrally disposed axially extending overlapping jointed segment means in said one end region of said casing, said segment means being yieldable toward the electrode in said casing.
 5. The invention set forth in claim 1 including: a. means defining a duct for conducting hot gas in heat exchange relationship with said casing, said duct surrounding at least the lower end portion of said casing, said hot gas effecting prebaking of said electrode material.
 6. The invention set forth in claim 5 wherein: a. said casing is vertical and said casing supporting means also supports said duct means, said supporting means being constructed and arranged for executing bidirectional vertical movements to thereby jointly move said duct, casing and electrode in relation to a furnace, and b. means for moving said supporting means.
 7. The invention set forth in claim 6 including: a. blower means for forcing heated gas generally downwardly along said casing means.
 8. The invention set forth in claim 1 including: a. means defining a duct surrounding said casing over a substantial part of its length, b. thermal insulation interposed between said duct and said casing in the upper portion thereof, the lower portion of said casing being uninsulated so that hot gas conducted by said duct will precure the electrode in the lower portion of said casing.
 9. The invention set forth in claim 1 including: a. a mantle surrounding said casing in spaced relationship to define a passage for heated gas, said mantle extending a substantial distance over the length of said casing, b. said mantle having an inlet for admitting heated gas to one end of said passage and an exit remote therefrom, and c. means for coupling a source of hot gas to said inlet.
 10. The invention set forth in claim 9 including: a. thermal insulation in said passage next to said casing and disposed to substantially limit heating of the paste in said casing adjacent to the one end portion thereof.
 11. The invention set forth in claim 9 wherein: a. said mantle is supported jointly with said casing by said supporting means, said supporting means being constructed and arranged for moving bidirectionally vertically to thereby enable joint movement of said mantle, casing and electrode in respect to a furnace, and b. means for moving said supporting means.
 12. The invention set forth in claim 11 including: a. blower means supported for moving jointly with said mantle for blowing said hot gas downwardly along said casing.
 13. The invention set forth in claim 1 wherein: a. said means for applying force on said electrode forming material comprises ram means adapted to register in said remote opening of said casing, and b. means operatively coupled with said ram means for forcing said ram means against said elEctrode material to expel said electrode from said casing and to retract said ram means to allow introduction of electrode forming material in said casing.
 14. The invention set forth in claim 13 wherein: a. said last named coupled means is a pressure operated cylinder.
 15. Self-baking electrode apparatus for use with an electric furnace, said apparatus comprising: a. a vertically disposed metal casing having a lower open end and an opening in its upper end for introduction of electrode forming material which becomes plastic and is successively baked to a hardened state in which it emerges from said lower end, b. support means for supporting said casing with its lower end positioned for cooperation with said furnace, c. clamp means constructed and arranged to bear against said electrode in its region of emergence where it is in a substantially hardened state, d. first means for applying a force on said clamp means to clamp said electrode against descending from said casing under the influence of gravity, and e. second means for applying sufficient force to said electrode through said upper opening in said casing to overcome the clamping force on said clamp means so as to cause said electrode to emerge further from said casing.
 16. The invention set forth in claim 15 wherein: a. said clamp means include a plurality of perimetrally disposed axially extending segments near the lower end of said casing, said segments being yieldable toward said electrode for frictional engagement therewith.
 17. The invention set forth in claim 15 including: a. means defining with said casing a passage extending along said casing over a substantial portion of its length, said passage being for conducting heated gas along the outside of said casing to prebake said electrode material therein, a portion of said passage being in intimate heat exchange relation with a lower end portion of said casing, and b. means for admitting heated gas to said passage.
 18. The invention set forth in claim 17 wherein: a. said passage defining means has an opening near the lower end of said casing for permitting gas to exit from said passage.
 19. The invention set forth in claim 17 including: a. means for moving said support means in opposite vertical directions, b. said passage defining means being supported by said support means and said casing being supported from said passage defining means whereby said electrode may be adjusted vertically with respect to said furnace to alter the distance between said electrode and contents of said furnace while said electrode remains clamped to said casing.
 20. The invention set forth in claim 15 including: a. a plurality of overlapping, axially extending segments firming the lower end of said casing, plate means disposed over the joints between the segments of said casing, b. electric contact means pressed against said plate means, c. said first force applying means acting on said contact means.
 21. The invention set forth in claim 20 including: a. means connected with said contact means for connecting said contact means to a source of electricity.
 22. Self-baking electrode apparatus for use with an electric furnace, said apparatus comprising: a. a vertically disposed tubular metal casing supported with its lower end in cooperative position relative to said furnace, b. the upper end of said casing providing access for introducing electrode forming material into said casing, said material being characterized by being in a plastic state when in a certain temperature range and by being cured to a hardened state when in a certain relatively higher temperature state, said electrode extending from said lower end of said casing in a substantially hardened state, c. means for frictionally engaging a portion of said electrode in a region where it is hardened substantially near the lower end of said casing whereby to restrain said electrode selectively statioNarily in said casing in opposition to the force of gravity on said electrode, and d. means for applying sufficient force to said electrode forming material at the upper end of said casing to overcome said frictional force and extend said electrode further from said casing.
 23. The invention set forth in claim 22 wherein: a. said casing includes means defining at least one overlapping joint at the lower end thereof to enable said casing to yield toward said electrode for said frictional engagement, b. means conforming substantially to the contour of said casing and disposed over said joint means, c. electric contact means in electric current exchange relation with said conforming means, d. means for applying a force on said contact means which is transmitted by the same to said plate means for causing said casing means to yield and effect said frictional engagement.
 24. The invention set forth in claim 23 wherein: a. said last named force applying means includes rigid ring means surrounding said contact means, b. plunger means supported on said ring means and projecting against said electric contact means, and c. spring means biasing said plunger means toward said contact means.
 25. The invention set forth in claim 22 including: a. a mantle extending a substantial distance over said casing and being in spaced relation therewith to define a gas flow passage, b. means for forcing heated gas through said passage longitudinally of said casing to thereby supply additional heat to said electrode material for prebaking the same.
 26. A method of making and using a self-baking electrode in association with an electric furnace, comprising: a. introducing unbaked carbonaceous material into the upper end of a vertically disposed tubular casing whose lower end cooperates with a furnace and from which lower end a baked and hardened portion of said electrode extends, b. directing heated gas over the exterior surface of said casing to prebake and cure said material near said lower end portion while at the same time heating said lower hardened portion by conducting current therethrough and by radiation and conduction of heat resulting from electric activity in said furnace, c. applying sufficient compressive force to a portion of said casing at the lower end thereof where said electrode is in a substantially hardened state to frictionally restrain said electrode against emergence from said casing under the influence of gravity, and d. periodically applying a vertically directed force on the material at the upper end of said casing to overcome said frictional restraint and cause said lower hardened electrode portion to extend further from said casing.
 27. The method set forth in claim 26 including: a. inserting wood core sections in sequence substantially centrally of said casing at the upper end thereof to provide a wooden spine through said electrode for strengthening the same, said unbaked carbonaceous material being inserted at the upper casing end around said core.
 28. The method set forth in claim 26 wherein: a. said heated gas has an initial temperature in excess of 450*C.
 29. The method set forth in claim 26 wherein: a. said electrode is baked at such rate that the hydrocarbon gases evolved from said carbonaceous material in the stages of baking near said lower end are prevented from escaping to said upper end by a vertically upward portion of said material being in a plastic state, whereby said gases are forced downwardly into the pores of the increasingly baked electrode portion. 